Method of evaluation for cooling ability of liquid

FIELD: measurement equipment.

SUBSTANCE: method is based on experimental determination of temperature of avalanching disintegration of cooling liquid on a hot surface, in static conditions, without liquid flow.

EFFECT: simplification of rejecting different lots of cooling liquid, decreasing amount of substance in investigated sample and consequently improved safety for personnel engaged in tests.

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The invention relates to a method of estimating the cooling capacity of liquids and presents a way to Express control of the adequacy of the cooling capacity of the liquid for any of the developed devices using different liquids, cooling high-heat components.

There is a method of estimating the cooling capacity of liquids on a special model plants flow type. He is to simulate the flow of the liquid under study in the most tallapragada section of cooling channel cooling device (Bolshakov GF Physico-chemical principles of the use of fuels and oils. Theoretical foundations of chemmotology at. - Novosibirsk: Nauka, 1987, str-92).

The disadvantage of this method is the lack of criteria dependences satisfactorily determine the conditions of the simulation of the processes occurring in the real models. Features cooling processes depend generally on physico-chemical and operational properties of the cooler, the speed of its flow, the initial temperature and the speed of its achievements, and therefore, the chemical composition at the entrance to the considered site tract, the material flow of the channel, the means of processing and surface condition, the geometry of the heat sink surface and the nature of the flow of the coolant. Under taccom modern flowing heat exchange units is the many of the above factors are equal for various parties investigated coolant that causes fuzzy cooling capacity for various parties coolant in the field of convective heat transfer. Further heating of the test section on units flow type detects the increase of the scatter of the experimental points (for various parties coolant) depending on the wall temperature on the specific heat flow and stratification of the corresponding approximating curves, which leads to the impossibility reliable estimates of the cooling capacity of the cooling liquid.

This phenomenon is explained by the change of physico-chemical state of the fluid due to the beginning of the bubble pseudocumene, and the temperature corresponding to the beginning of the intense heat turning cooler, the so-called "destruction", the end products of which among others are solids generated during the decomposition of the cooler, and during its reaction with the impurities included in its composition. The reaction can join and intermediate products of the reactions of decomposition of the cooler. These products, which are deposited in the form of consobrina formations on the walls of the cooling tract, significantly increased thermal is soprotivlenie heat-release surface, changing as education sediment layer, its accumulation and possible entrainment by a turbulent flow. The result is overheating of the surface to be cooled and its destruction, which in turn can lead to violation of the workflow in the sample technique.

The purpose of this invention is to provide a comparative methodology for estimating the cooling capacity of liquid in stationary conditions compared with the sample fluid, the required cooling capacity is installed in field tests. Quantitative quality control of coolant on the proposed method correlates with physically reasonable value of the temperature of the beginning of intensive thermal decomposition of the coolant.

This goal is achieved by the fact that the comparative determination of the quality of the coolant is conducted on experimentally installed in static conditions, the dependency of the temperature of the heat-release surface from the time when the last temperature avalanche collapse of a cooling liquid on a hot surface, without fluid flow, in comparison with the same dependence, but for the sample of the coolant, a sufficient cooling capacity is installed.

Setup that implements the proposed method estimates the cooling capacity of the LM the bones, consists of the following main parts (see drawing):

- capacity for the analyzed fluid displacement 350 cm3designed for working pressure PP=16 MPa ("bomb"), pos.2;

- a step-down transformer for heating the experimental tube electric current, 3;

regulating transformer, pos.17,

three tanks with a volume of V=0.5 l each for filling and draining the liquid under study, pos.4,9,16;

- a can of compressed nitrogen for pressurization, pos.6.

All elements of the unit is made from a material IN, as the sealing material is a fluoroplastic-4 and aluminum. The plant is equipped with shut-off, pressure relief and drain valve.

Fuel element (experimental phase)inside the working tank and immersed in the test liquid, is heated by an alternating electric current tube diameter of 3.0×1.5 mm, and the length of the heated part 400 mm, made from steel 18CR10NITI (to study the catalytic effect of structural material for the process may use other materials and alloys). As the fuel element can also be used membrane in the measuring cell of special construction, having two cavities.

Experimental section is equipped with two thermocouples HC: on the inner surface in the center of the tube (the temperature value T2) and 4-5 mm above the outer surface of the tube, directly in the liquid (temperature T1).

The proposed method of assessment (test) quality of the coolant based on the fixing temperature increase of the inner surface of the tube by means of a thermocouple in time for xed values of electric power, providing virtually instantaneous temperature reaches the beginning of its destruction. The increase in thermal resistance, irrespective of its cause causes and the growth temperature of the inner surface of the element at a constant heat load due to the deterioration of heat exchange with the investigated liquid.

The principle of creating a test setup based on a static method, in contrast to dynamic, contributes to the solution of important problems: minimizing factors that affect the relationship heated surface-chemical conversion of fuel at high temperatures and pressures in contact with her. In traditional ("running") methods such factors very much, that does not allow us to establish the specific behavior of the actual component.

It should be noted that the proposed method comparative characterization of various parties fluids, providing a greater or lesser extent, the impact on the cooling properties, is intended to facilitate the process of rejection of various parties cooling fluid is involved in its production, storage and use. Thus, verification is the specific component composition (including microtrace), in one way or another affecting such traits as cooling capacity.

Since the proposed method is designed to generate conclusions "worse"to"better", the exact value of the temperature of the beginning of thermal decomposition does not matter, because at this stage it is not the aim of studying the process of heat exchange in the light of all history (e.g., decomposition). You only need to enter temperature mode, guaranteeing the flow of this process.

Permanently installed on-site heat load, excluding additional adjustment improves the accuracy of determining the rate of heating due to the elimination of possible methodological errors in the course of achieving a work area of the fixed temperature of the beginning of the destruction.

Thus, as the criterion (comprehensive index)characterizing OS coolant, offered the rate of internal heating surface of the heating element.

Processing of results of measurements can be carried out as follows. On the removed tape recorder is applied on scales of temperature and time scale, then set the initial "zero" time, with testwuide temperature T2. Tape recorder with 0.5 removed with the appropriate values of time and temperature T2.

The obtained temperature information (T2) and time are processed according to a special formula.

The data obtained depending on the temperature T2 higher than the temperature of thermal decomposition process by the method of least squares and obtain the parameters of the approximating straight line:

Y=a+BX.

Odds are, with this method of processing the results, is the desired complex indicator of the cooling capacity of the coolant, and can be used to characterize the quality of the product.

The sequence test setting (drawing):

1. Prepare the setup for the measurements.

The original position. The source is the following

position position:

- previously, the sample fluid flushed;

- product line ready for filling;

- pressure in the system is missing;

- gearbox posr displayed;

- all valves B1-B11 are closed.

- instrumentation is disabled.

Check the tightness of the installation produced in the following order: open B6, gear P1 (POS) on the pressure gauge (POS), set the system pressure P=100 kg/cm (1.25 rrab). With closed valves B1 and B6 gauge control g is reticent exposure for 15 minutes In the presence of leaks can be checked by emiliania connection setup.

2. Refill coolant.

Checked for leaks install dressed cooling fluid through the valves B1 and B2 from the tank pos.4. Filling is as follows:

- open the valves B1, B4, B7;

- include a vacuum pump (pos.8). The system creates a vacuum (control manufacyurer POS, indications or minus 1.0 kg/cm2);

- close valve V7, open valves B3 and B2;

- after exposure installation in this state for 1 min close the valves B1, B2, B3.

3. The measurements.

The measurement is carried out in the following sequence:

- opens the valve B6 and using gear P1 is set to a pressure of 80 kg/cm2) in the vessel 5. Pressure is controlled by a manometer (POS). At the end of the pressurization valve B6 is closed:

- open valve V7;

- enabled devices KSP-4 to register the current values of the temperatures T1 and T2 (10 and 11) and time;

- batch switch on the measuring tube is the desired voltage (8 V) and current (140 A), creates a given heat load equal to 1.12 kW;

- upon reaching the temperature T2 of the temperature values of thermal properties of the investigated coolant controlled in salino by reading the respective device KSP-4, is the shutter speed for 3 seconds Recorded current and voltage in the heating tube instrument position 12 and 13,

- closes the valve V7;

- off devices KSP-4;

the heating tube is de-energised.

Measured values are the temperature of the inner surface of the heating pilot tube from the time (T2)taken from a tape recorder.

4. Return to the original position.

Return the original position is performed in the following sequence:

- opens the gate B5 and reset the pressure in the system through capacity for waste flow (pos.7) and discharge capacity (pos.9);

after reaching the measurement site temperature (20+5)°With the valve 5 closes and opens the valves B1 and B9;

- opens the valve B6 and gear P1 (POS) creates a pressure in the buffer tank (5) P=0,na;

- opens the valve V7 and the cooling liquid from the measuring node perelavlivaet in drain capacity (pos.9);

after draining component all valves are closed;

the gear P1 is displayed, the instrumentation is de-energized.

5. Neutralization product lines.

Neutralization product line is made after completion of the sample fluid and in the event of an interruption in the work on the sample more than one day

Neutralization is performed in the following sequence:

Opens the valve B6 and gear P1 (POS) creates a pressure in the buffer tank (5) P=0,mA.

Open the valves V7, B1 and B9 and is made within one minute to purge the lines with compressed nitrogen.

Produced two consecutive operations of filling and draining of the acetone from the product lines (at the above section "Filling the coolant, where the role of the valves B2 and B3 perform valves B10 and B11, respectively).

From valve 10 is detached tank with acetone and otstykovyvatsya similar capacity with alcohol.

Produced two consecutive operations of filling and draining of the alcohol from the product line.

Performed a second operation purging the lines with compressed nitrogen.

The measurement result is the dependence of the temperature on the inner surface of the heating pilot tube from time to time, removed from the tape recorder.

Implementation of the proposed method is as follows. Originally manufactured by removing the dependence of the temperature on the inner surface of the heating experimental tube over time for a sample of the coolant with the installed cooling capacity (i.e. cooling capacity which meets the requirements). Then removing the depending of the temperature of the inner surface of the heating experimental tube over time for a sample of the coolant, the cooling capacity which need to be evaluated. This is followed by a comparison of the obtained experimental data on the basis of which a conclusion is made about the suitability of the sample coolant to use.

The advantages of using this method is a simplification of the process of rejection of various parties coolant, reducing the number of substances in the test sample, which in turn ensures the safety of personnel conducting the studies, when using corrosive and toxic liquids and stores the model in the processes of heat transfer (sufficient heat to the heated fluid).

The method of estimating the cooling capacity of the liquid, in which the evaluation of the cooling capacity of the liquid is made on the basis of experimental determination of the temperature avalanche collapse of a cooling liquid on a hot surface under static conditions, no fluid flow through the comparative determining the quality of the coolant in dependency of the temperature of the heat-release surface from time to time in comparison with the same dependence for the sample of the coolant with the installed cooling capacity.



 

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